Carb Question

the velosity of the air ( or expansion) going thru it... Like an air conditioner spraying freon thru an orifice.. as it EXPANDS it gets very cold..

Edited by steve(ill) - 06 Dec 2025 at 12:23pm

So is there a cure?

some use sheet metal guards to cover the carb and exhaust manifold and get some heat in the area ... preheating the air into the air cleaner could help ... maybe under hood intake..

Les Kerf wrote: Gary Burnett wrote: So is there a cure? Our vintage tractors are not well equipped for dealing with carburetor icing. The cure is to introduce heated air into the air stream ahead of the carburetor. I have driven old Ford pickups that have the 300 cubic inch inline six engines for the past 40+ years, these reliable old workhorse engines are notorious for carburetor icing unless the thermostatically controlled hot air stove on the exhaust manifold is properly connected to the air cleaner and fully functional. I prefer the early 1980's 300-6 pickups because I can buy them cheap since almost everyone thinks they need a V8. Of the five I have owned, only one had a fully functional air cleaner because the previous owners (all named Bubba) thought they were smarter than the Ford engineers who designed them   Yup, they iced up until I could get the hot air stoves working. The worst conditions for icing are generally when the air temperature is just a few degrees above freezing with high humidity and cruising at fairly high intake manifold vacuum.

Had a 1980 F150, 300 6, 4 speed manual. Yes, the engine never gave one hint of trouble but had 3 various transmission issues in the time I owned it which was 5 1/2 years. About then I got my first big boy job and bought a new car. My father in law was on hard times so I gave him that truck (right after I replaced the radiator). He drove it a few years until it rusted out so bad he was dragging the gas tank down the road by the fill hose. Never an engine problem though! But holy cow did it rot away. Hard to believe there’s any of them on the road past 20 years old, but I do see them from time to time.

DrAllis wrote: I had a Ford LN-800 medium duty truck decades ago, equipped with a Super-Duty 477 V-8 engine. I always would start the engine and give it a few minutes of warm-up time before heading down the road. Two or three times a year, if the ambient temp was just right, the humidity was just right, the barometric pressure was just right, the dew point was just right and the moon phase was just right, as it warmed up, it would slowly frost over under the big HOLLEY 4BBL carburetor, and literally choke itself dead. All you had to do was just wait a few minutes for the frost to dissipate and fire it up and awaaay we go !!!

Yep, back in High School days, worked for the local BTO(by those days standards), they had a Farmall 560 that was notorious for carb ice. Any cloudy day, below 50 degrees, humid. That thing would ice over on its first startup for the day. Would choke itself off, let set 5-10 minutes, restart then good for the day.

NEVER green wrote: Tbone95 wrote: Les Kerf wrote: Gary Burnett wrote: So is there a cure? Our vintage tractors are not well equipped for dealing with carburetor icing. The cure is to introduce heated air into the air stream ahead of the carburetor. I have driven old Ford pickups that have the 300 cubic inch inline six engines for the past 40+ years, these reliable old workhorse engines are notorious for carburetor icing unless the thermostatically controlled hot air stove on the exhaust manifold is properly connected to the air cleaner and fully functional. I prefer the early 1980's 300-6 pickups because I can buy them cheap since almost everyone thinks they need a V8. Of the five I have owned, only one had a fully functional air cleaner because the previous owners (all named Bubba) thought they were smarter than the Ford engineers who designed them   Yup, they iced up until I could get the hot air stoves working. The worst conditions for icing are generally when the air temperature is just a few degrees above freezing with high humidity and cruising at fairly high intake manifold vacuum. Had a 1980 F150, 300 6, 4 speed manual. Yes, the engine never gave one hint of trouble but had 3 various transmission issues in the time I owned it which was 5 1/2 years. About then I got my first big boy job and bought a new car. My father in law was on hard times so I gave him that truck (right after I replaced the radiator). He drove it a few years until it rusted out so bad he was dragging the gas tank down the road by the fill hose. Never an engine problem though! But holy cow did it rot away. Hard to believe there’s any of them on the road past 20 years old, but I do see them from time to time.   Very strange to have issues with Ford manuals, usually bullet proof.  The 300 has been voted the most reliable engine on many polls.    Chevy ran Ford Top loader trannys  (not a pronoun) for yrs in NASCAR, their rock crusher Muncies did not hold up.

Well, I don’t know what the deal was. Maybe a lemon. The guy who fixed it a couple of the times told me that the tranny was built in Mexico and everything about it was cheapened up. When I bought it it was 4-5 years old but I don’t recall the mileage. Not a lot. I also don’t know what the original owner used it for to know if it was abused, but from what I know about him I doubt it was used hard. I used it pretty much like a car. Very rarely hauled any more than a few suitcases in the back. Most miles were highway. It was so under carburetor-ed it didn’t have enough power to hold speed up a hill.

Anyway, first time it was howling awful. Carrier bearing. I suppose I could have lived with that for a while but it was pretty annoying on a 3 1/2 hour drive. This actually happened twice.

It would pop out of 4th gear while going down a hill. I never had that addressed.

One night I was almost to my place, in second gear, pushed in clutch and pulled shifter to neutral, and “bang”! Wtf was that? Hmm, stuck in 2nd. Turns out a pin broke and came out and whirled around inside and screwed a bunch of stuff up.

Then 1st gear went out, like you’d try to take off and it wouldn’t stay in gear. That was near the end.

Must be a regional issue. Growing up in Arizona I didn't know ice, frost, humidity and rust were in the English language!